Combined infrared and Raman study of the optical phonons of defect chalcopyrite single crystals

Infrared and Raman investigations of CdAl2Se4, ZnAl2Se4 and ZnIn2Se4 single crystals with respect to the optical phonon mode activities predicted for space groups I (4) over bar and I (4) over bar 2 m are reported. Variations of the cation and vacancy distributions affect the infrared reflectivity s pectra more pronounced than the Raman spectra of the compounds. To decide w hether the compounds crystallize in space group I (4) over bar or I (4) ove r bar 2 m by means of optical spectroscopy both infrared as well as Raman s pectroscopy have to be used. (C) 1999 Elsevier Science B.V. All rights rese rved.